The present invention relates to a process and to a device for the jigging of a flat can in a textile draw frame. The jigging influences the depositing of the fiber sliver. If errors occur in the depositing of the fiber sliver, this has harmful repercussions on the withdrawal of the fiber sliver. The time it takes to fill a can is determined by the possible delivery speed of the fiber sliver and the jigging speed of the flat can which is correlated to it. The quality of the fiber sliver depositing is thus also determined by the manner in which jigging takes place.
The form of a flat can is essentially different from that of a round can. The flat can has a rectangular area, with the long sides being delimited by narrow forward sides. The flat can is equipped with a can tray capable of being moved vertically. The can tray is positioned below the upper can rim when empty.
According to the state of the art, the flat can is filled by moving the flat can back and forth, i.e. by jigging it, while the delivery device (rotary plate) remains stationary.
The fiber sliver is deposited cycloidically over the length of the movable can tray. Several such layers of deposited fibers constitute a fiber column.
During the translation of the flat can, its speed is synchronized with the speed of the delivery device. The back-and-forth movements of the flat can take place at a constant speed up to the point of reversal. Until now it was common practice to move the flat can with a constant speed value as it is being jigged, i.e. the flat can strikes the limit stop constituting the reversal point at a constant speed. The limit stop is here of such dimensions that it absorbs the dynamic energy of the flat can. For this reason it was important to achieve an extremely rapid reversal of direction, as much as possible without any delay, in order to move the flat can immediately with a corresponding speed value in the opposite direction.
The sudden reversal of the movement has as a consequence that the fiber sliver column in the flat can is very much shaken and sways. Abrupt speed or acceleration changes occur at the reversal point. This expresses itself in violent impacts on the flat can. Such periodic impacts disturb the depositing of the fiber sliver and eventually the build-up of the fiber sliver column. The fiber sliver is pushed out of the desired depositing path at the forward sides of a flat can by these impacts. Such disturbances increase the danger of sliver breakage as the sliver is withdrawn.
The translation movement furthermore results in heavy swaying of the fiber sliver column at the reversal points, and this also interferes with the depositing of the sliver loops at the forward sides of the can. Swaying briefly creates gaps between sliver column and side. The sliver loop may be knocked into this gap during reversal and may become wedged. This interferes with the depositing of the fiber sliver and the build-up of the sliver column.
For these reasons it was not possible to increase the delivery speed of the fiber sliver significantly when filling a flat can.
Neither is this possible with the solution according to DE-AS 1158420 and DE-AS 1923621, since they already have the above-mentioned shortcomings. The solution according to DE-AS 19 23 621 therefore merely intends to create an improved process for the depositing of fiber slivers in rectangular cans. As DE-AS 19 23 621 (column 3, lines 48-54) explains, increased filling of a rectangular can is achieved thanks to the cycloidically deposited windings and the paths of the windings lying next to each other in a special zig-zag or meandering fashion, while the initially mentioned disadvantages are not eliminated. DE-AS 1158420 has the special feature that a depositing container (cardboard box) is installed on the conveyor rollers of a platform during the filling process, with the conveyor rollers having no function in the jigging of the depositing container.
DE-AS 291895 proposes to stop a container on a plate during filling, the plate being displaced by means of a coordinate-controlling control device. The coordinate-controlling device is merely able to control the XY coordinates of the plate in accordance with two mechanical control curves. One single speed is set and maintained for the filling process.
EP457 099 recognizes that relatively large masses of fiber sliver are moved during the back-and-forth movement of a flat can as it is being filled. In the known process the speed of the translation movement of the flat can is increased briefly before reaching the reversal point and is returned to a predetermined translation speed after reaching that point (column 4, lines 56-58, column 4, lines 1-4). It has not been possible to prevent the depositing of the sliver loop from being disturbed at the front.
The process solutions according to the state of the art are thus not suited to achieve undisturbed depositing over the entire height of the can near the front of the flat can. Neither was it possible in this connection to increase the depositing speed. Because of these shortcomings, it was not possible to achieve the depositing speed of the fiber sliver which can already be achieved with round cans.
The device for the filling of a flat can is equipped with a travelling carriage arrangement to support the flat can according to DE-AS 19 23 621. The carriage arrangement consists of an upper and a lower carriage which are moved automatically under the influence of a programming device and of control devices. The can is placed on the upper carriage. A rotary plate is stationary above the can and delivers the fiber sliver. The can is held by the lower can sides on the upper carriage. This has the disadvantage that an undesirable force moment is exerted upon the can sides and the can tray of the can as the fiber sliver column sways as a result of the can movement.
The basic disadvantage of such filling devices is however the fact that a relatively large mass must be moved back and forth. This mass is not only constituted by the flat can, but especially also by the supporting platforms or the carriage structure. Drive and drive elements are thus subjected to great stress.
The device according to EP 457 099 avoids this disadvantage in that the cans are suspended from a conveying device. The conveying device is equipped for that purpose with detachable holding elements from which the flat can is suspended. These holding elements are made in the form of graspers interacting in pairs which are capable of swivelling around their vertical axis. The graspers grasp the flat can near the upper can rim and on the narrow side.
Although this device makes it possible to use a slightly higher translation speed than do the solutions according to the state of the art, it nevertheless does not prevent interference with the sliver loop near the front during the depositing process.